Lactic Acid – Fact or Fiction?

This morning, while I researched new topics to discuss, I came across this astonishing answer to a question posted on Yahoo Answers. The question was in regard to the reason for muscle soreness after exercise. The top voted answer to said question is as follows:

“The muscle pains could just be a build up of lactic acid. When you do physical activities your body uses oxygen and glucose (aerobic respiration). When doing harder work, not enough oxygen will get to your muscles so they go into anaerobic respiration. This makes a build up a lactic acid. That’s what I think anyway.”

As a (soon to be) exercise physiologist, I am distraught by this answer. The first sentence is where it all goes wrong. Thereafter his/her explanation of cellular respiration is quite simplified, however valid. For some reason, people still assume that lactic acid build up is what causes muscle soreness. Over ten years ago, this was the thought. I can still vividly remember an episode of The Magic School Bus (one of my favorite childhood TV shows) where Mrs. Frizzle had sore calves and stated that lactic acid was the problem for her soreness. Has this misguided paradigm lasted this long?

What is Lactic Acid?

As the respondent suggested, it is the byproduct of cellular respiration when there is not enough oxygen being transported to the working tissue. Thus, this accumulation of lactate does occur as a result of prolonged anaerobic respiration.

Previous scientific literature suggested that lactate (or lactic acid) was only broken down by the liver through the Cori Cycle and by the heart for energy. Current research (within the last 10 years) has identified that local muscles can also metabolize excess lactate for energy. Therefore, lactate is another source of energy by the body which is in abundance during prolonged anaerobic respiration.

Why has Lactic Acid been thought to cause muscle soreness?

A buildup of any acid within the blood or tissue is referred to as acidosis. It was thought that a buildup of lactic acid can cause acidosis, however recently it has been shown that lactate acts as a buffer and other processes in cellular respiration are at fault for causing acidosis. Therefore the once believed to be cause of muscle soreness has been discredited by science, however people still hold true to the notion that muscle soreness and lactic acid are related.

What causes muscle soreness?

Since it cannot be lactic acid, what is it then? The true reason for muscle soreness or delayed onset muscle soreness (or DOMS for short) has yet to be sufficiently determined. One of these theories is due to the inflammatory process associated with recovery. During exercise, you produce micro tears within the muscle and those need to be fixed through the inflammatory process. The healing process causes decreased flexibility of the muscle and heightens pain sensation so that you stay mobile.

The second theory is that increased intracellular acidosis occurs (not be production of lactate) in conjunction to increased intracellular calcium. This theory is based off of sustained physical exercise (endurance based exercise) as the mitochondria within muscles (energy powerhouse) will be overwhelmed and become exhausted).

How to treat muscle soreness?

If you have ever suffered from DOMS, you know the debilitating pain. It can last for up to 72 hours of shear agony causing you to weep when you have to get out of your chair, go down a flight of stairs, or even reach for the top shelf of a cupboard. Here are a few simple ways to reduce the amount of DOMS one might sustain after a tough exercise bout: